Multiplex radiotelegraph system



Aug. 28, 1923. 1,465,932

, E. H. COLPITTS MULTIPLEX RADIO TELEGRAPH SYSTEM Original Filed Sent. 11, 1915 -q v 22 zafl I 27 4 a 7 M 9 l6 I l 3 am 2 mm 2,

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35 A 5 g2 Z [a sent generators of high frequency low ower Patented Aug. 28,1923. I

UNITED STATES PATENT OFFICE.

EDWIN H. COLPITTS, OF EEAS'I ORANGE, NEW JERSEY, ASSIGNOB, BY MESNE ASSIGN- MENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION 01? new roan.

MULTIPLEX EADIOTELEGRAPH SYSTEM.

Application filed September '11, 1915, Serial No. 50,172. Renewed November 2, 1920. Serial No.'421,764.

To all whom it may concern:

Be it known that-I, EDWIN HENRY Cor.- Prrrs, a subject of the King of Great Britain, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Multiplex Radiotelegraph Systems, of which the following is a full,'clear, concise, and exact description.

.This invention relates to the transmission and reception of signals, and more particularly to multiplex telegraphy whereby a plurality of neously from one or several stations and may be received simultaneously on one antennav or on a plurality of antennas located at the same place or at various places.

One of the objects of the invention is to overcome the difficulties encountered in making and breaking, for signaling purposes, circuits carrying large power. A further object is to avoid, in multiplex radio signaling systems, the duplication of apparatus of large size for the production of power of different frequencies. These objects are obtained. by using a plurality of generators of high frequency oscillations of, low power, controlling the power from. these generators in accordance with signalsto'be transmitted and then amplifying this controlled and modulated power.

A further object is to receive the plurality of signals separately and without confusion,

and to this end use is made of a source of high frequency oscillations at the receiving station, which oscillations combine with the received oscillations to give a beat fre 'uency of a definite period. Oscillations of this beat frequency can then be received with high selectivity by apparatus both clectrically and mechanically tuned to this beat frequency.

Referring to the drawings: Fig. 1 shows a transmitting station; Fig. 2 shows a receive ing station to be used in conjunction with.

such a station as is shown in Fig. 1; Fig. 3 shows a modification of the circuit shown in Fig. 2. In these fi res, 4, 5 and 6 repreoscillations. These generators may e of any suitable type, such as dynamos, mercury vapor osclllation generators or thermionic oscillation generators of the audion type.-

Each of these generators is supplied with a signaling key 7 and all are connected in paral el to the input circuit of a thermionic messages are transmitted simulta- .placed in the input circuit as shown to de' termine the potential of the grid 1O, and a battery 13 is placed in the output circuit for supplying the power necessary for said output circuit. The output circuit of this am-- plifier is connected by means ofthe transformer 14 to the input circuit of a power amplifier 15., This power amplifier, which in general will consist of a plurality of tubes connected in parallel, is here shown diagrammatically and possesses the usual heated element 16, grid 17 and plate 18. The input circuit includes the battery 19, and the output circuit includes the battery 20. The manner of connection and operation of this power amplifier is fully set forth in patents to Arnold 1,129,942 and 1,129,943.

To the output circuit of this power am-' ductor 200, which is connected to ground In order to improve'the efficiency of radiation, it has been found desirable to give this radiating antenna a number of degrees of freedom agreeing with the number of messages to be transmitted. The increase in the number of degrees of freedom is obtained by making this antenna system more complex, and one method for doing this is shown in Figure 1, in which 22, 23 and 24 show reactances connected in parallel to each other and in'series to the elevated conductor 200. In view of these degrees of freedom imparted to the radiating system it is possible to tune the antenna to each and all of the frequencies to be'used for signaling. In

this case it is also desirable to ive the output circuit of the power amplifier an equal. number of degrees of freedom, one method for accomplishing which is shown by insertingthe condensers 25, 26 and the inductance .27, in the manner shown.;

sary degrees of freedom being supplied in the same or sar manner as at t e sending station=-namely, by means of the con-v densers 36, 37, and the inductance 38. A plurality of receiver circuits, connected in parallel with respect to each other, are

connected to the tuned circuit 36, 37 .These.

receiver circuits are identical in form, each comprising a thermionic detector 40, whose 1 input electrodes ell, 42 are connected to the tuned circuit 36, 37. The output circuit, including the electrode t3, contains the usual batte'ly it and the primary of a transformer 45. be secondary of this transformer is 115 connected in series with the condenser 46 and'a translating device 47. Inductively connected to the input circuit of the detector by means of the transformer 50 is a genorator of high frequency oscillations 51.

This generator is so regulated that the freguency of oscillations produced thereby difers slightly from the frequencies of the generators ll, 5 and 6 at the transmitting station.

The operation of the system is as follows:

Generators fit, 5 and 6, adjusted to generate oscillations of a. certain definite frequency, difier the one from the other: for examplethese may be 100,000, 99,600, 99,200 and so forth. Upon the closing of one or more of the signaling keys 7 oscillations of the frequencies of the corresponding generators will be im ressed upon the input circuit of the ampli er 8. This amplified power will then be impressed uponthe input circuit of the power amplifier 15, that is, all the power high frequency oscillations of differ- 0 example, the generator 4i: has a frequency of 99,600 and signals'are sent from this gem.

.erator, then there will be impressed upon the input circuits of thedetectors 40 high frequency oscillations which have a beat frequency of 600, and the oscillations which are then set up in the output circuit of those detectors will have a frequency of 600.

The circuits containing the translating devices are electrically tuned by means of the condensers 46 and the inductances of elements 47 in the circuits to a frequenc equal to the beat fr uencies. One sue circuit, for example, wi 1 be tuned to a frequenc of 600, another circuit will be tuned to a requency of say 200, and so forth.

antennae Only that. circuit then which is tuned to a frequency of 600 will take up or select signals transmitted from the generator it. In this manner signals sent from any of the generators will be picked up by one and oniy one receiving circuit.

order to increase the selectivity of the circuits containing the translating devices, it is desirable to have the translating device mechanically tuned to the frequency to be received. This may be accomplished in a variety of ways such, for example, as hav-.-

ing a telephone receiver with a tuned dia-;,

phragm or by tuning forks, or by any other suitable and well-lmown expedient. Fig. 3 shows a modification of the receiving c rcuit in which but one'detecto'r 52 is used, this detector being of the same type as those shown in Fig. 2. Connected 1n the output circuit of said detector 52 is a high im edance 53, and connected in shunt to such impedance 53 are a plurality of re. ceiver circuits, each electrically tuned to a certainbeat frequency and having a re-' ceiver mechanically tuned to the same beat frequency in the same manner as the receivin arrangement described in connection with Fig. 2. The modification shown in Fig. 2 has the advantage that in view of the unilateral nature of the detectors l0 there can be no back reaction from onetranslating circuit into another. This disadvantage in the case of Fig. 3 may be diminished by the use of such tuned weeding-out circuits as are described inpatent to Stone 714,756, December 2, 1902, or other systems used for the same purpose.

lit is obvious that in case the signals received are very weak, the detectors 4:0 and 52 may be adjusted to act also as amplifiers or that separate amplifying devices may be inserted in the circuits for this purpose.

While but three generators and receiving circuits have been shown, it is obvious that any number may be used.

In Fig. 1, a single voltage amplifier 8 has been shown which feeds by means of the transformer 14 into the power amplifier 15. It is to be understood, however, that a plurality of these voltage amplifiers 8 may be connected in series to step up to a higher voltage, in the manner described in the patouts to Arnold mentioned above.

A in the ordinary case the antenna may be replaced if desired by a transmission line.

Although this invention has been described'as particularly applicable to multiplex' radio telegraphy, it is obvious that certain features of the invention which are covered by the appended claims are capabio of application generally toenergy wave transmission for signaling or selective purposes, regardless of the medium.

What is claimed is: Y L- The method of transmission which "local means for simultaneously impressing comprises simultaneously transmitting energy of a plurality of different frequencies, combining therewith energy of a different frequency and causing the combination frequencies produced thereby to selectively'operate a plurality of devices.

2. The method of multiplex signaling which comprises simultaneously transmitting energy of a plurality of different frequencies, combining therewith energy of a different frequency and causing the combination frequencies produced thereby to give signal indications.

3. In a transmission system, a receiving vdevice, means for simultaneously impressing thereon received energy of-a plurality of frequencies, local means for simultaneously impressing upon said device energy of a different. frequency, and individual means operative in response to beats set up by said device between said local energy and received energy of each of said frequencies.

4. In an electric transmission system, a receiving circuit, -means .for impressing thereon received fluctuating energy of a plurality of frequencies, local means for impressing thereon an electromotive force of a different frequency and separate means associated therewith for indicating each of a plurality of different frequency beats produced thereby.

5. In an electric transmission system, a receiving circuit, means for simultaneously impressing thereon received fluctuating energy of a plurality of high frequencies,

upon said circuit an electromotive force of a different high frequency and individual means for utilizing each difierence frequency current produced by said received energy and said locally impressed electromotive force. I

6. In-an electric transmission system, a receiving circuit, means for simultaneously impressing thereon received fluctuating energy of a plurality of high frequencies, local means for simultaneously impressing upon said circuit an electromotive force of a different high frequency, and means for utilizing energy of the beat frequencies set up by the interaction of current from said local source and said fluctuating energy.

7. A signaling system comprising means for simultaneously supplying a plurality of message waves of different frequencies, means for supplying, oscillations. of a single frequency for combination with said waves, meansfor combining said waves and said oscillations, and means for utilizing the combination frequency oscillations thus produced.

8. A transmission system comprising. a receiving element, means for simultaneously impressing thereupon a plurality of energy wave trains each of said trains having a frequency individual thereto, means'associated with said element for combining with said received energy, locally produced oscillations of a single frequency, and individual means acting in response to the combination of each different frequency wave train with said locally produced oscillations.

9. In a multiplex radio signaling system,

a receiving station adapted to receive simultaneously a plurality-of messages transmitted by means of oscillations of differentwave lengths, said station comprising a reccivingantenna; a local generator of oscillations differing slightly in frequency from the signaling frequencies; a plurality of receiver circuits and translating devices in said circuits, each of said circuits being tuned to the beat frequency of the locally generated oscillations and the oscillations received from a corresponding sending sta- 7 tion.

10. In a multiplex radio signaling system, a plurality of generators of low power 03- cillations of high but differing frequencies;

signaling means for controlling said gener- 4 ators in accordance with signals to be transmitted; means for amplifyingsaid oscillations; an'antenna for radiating said amplified oscillations; a receiving-antenna; a local generator of oscillations differing slightly in frequency from the signaling frequencies; a plurality of receiver circuits and translating devices in said circuits, each of said circuits being tuned to the beat frequency of the locally generated oscillations and the oscillations received from a correspending generator at the sending station. i

11. In a multiplex radio signaling sys term, a receiving station adapted to receive simultaneously a plurality of messages transmitted by means of oscillations of difcontaining a detector and a translating device in the output circuit of each of said detectors, eachoutput circuit being electrically tuned to'the beat frequency of the 10-- cally generated oscillations and the oscillations received from a corresponding sending station. I v I 12. In a'multiplex radio signaling system, a plurality of generators of low power oscillations of high but differing frequencies;

signaling means for controlling said generators in accordance with the signals to be transmitted; an antenna for radiating said oscillations; an antenna;- for receiving said ferent wave lengths; said station comprisoscillations; a local generator of oscillations .difiering slightly in frequency from the signal frequencies; a circuit on which the received oscillations and locally generated osceived from a corresponding generator at the sending station.

13.- In a multiplex radio signaling system, a plurality of generators of low power oscillations of high but difiering frequencies; signaling means for controlling said generators in accordance with signals to be transmitted; means for amplifying the oscillations; an antenna for radiating said oscillations; an antenna for receiving said oscillations; a local generator of oscillations differing slightly in frequency from the signal frequencies; a circuit on which the re ceived oscillations and locally generated oscillations are impressed and a plurality of receiver circuits associated with the last named circuit, each of said receiver circuits containing a detector and a translating device in the output circuit of said detector, each output circuit being electrically tuned to the beat frequency of the locally gen erated oscillations and the oscillations received from a corresponding generator at the sending station.

14. In a multiplex radio signaling system, a plurality of generators of low power oscillations of high but differing frequencies; signaling means for. controlling said generators in accordance with signals to be trans mitted a thermionic amplifier of the audion type; a radiating antenna; the input circuit of said amplifier being connected to the generators and the output circuit being inuctively connected to the radiating antenna; a receiving antenna; a local generator of oscillations difiering slightly in frequency from the-signaling fre uencies; a circuit 'onwhich the receive cillations and the locally generated oscillations are impressed and a plurality of receiver circuits associated with the last named circuit each of said receiver circuits containing a thermionic amplifier of the audion type and being tuned electrically to the difierences between the locally genen 'ated frequency and-the frequency of a den responding generator at the sending station, and a translating device associated with each of said plurality of circuits and tuned mechanically to the frequency of its circuit. i

15. la a "multiplen-- radio signalimg system, a plurality'of generatorsof low power incense oscillations of high but difiering frequencies; signaling means for controlling said generators in accordance with signals tobe transmitted; a thermionic amplifier or amplifiers, of the audion type; a radiating antenna tuned to the fr uencies of the enerators; the input circuit of said ampl' are being connected to the generators and the output circuit being inductively connected to the radiating antenna; a receiving antenna tuned to the frequencies of the generators; a local generator of oscillations-differing slightly in frequency from the signaling frequencies; a circuit on which the received oscillations and the locally generated oscillations are impressed and a plurality of receiver circuits associated with' the last named circuits, each-of said re-.

' electrically to the difference between the 10- cally generated frequency and the frequency of a corresponding generator at the sending station, and a' translating deivce associated with each of said plurality of circuits and tuned mechanically to-the frequency of its circuit. p

16. In a multiplex radio signaling system, a receiving station adapted to receive simultaneously a plurality of messages transmitted by means of oscillations of difi'erent wave lengths, said station comprising a receiving antenna; a local generator of oscillations differing slightly in frequency from the signal frequencies; a plurality of receiver circuits tuned electrically to the beat frequency of the locally generated. oscillations and the oscillations received from a: corresponding generator at the sending station; and a translating device associated with each ofsaid plurality of circuits and tuned mechanically to the frequency of its circuit.

17. A signaling system comprising a receiving circuit, means including frequency selective elements for simultaneously supplying said circuit with a plurality of message waves of difieren-t frequencies, local means for impressing oscillations upon said circuit, and a second receiving circuit connected to said circuit, said second circuit beindications.

- 18. A signaling system comprising a receiving circuit, means including frequency selective elements for simultaneously supplying said receiving circuit with a plurality of mes v sage waves of difierent frequencies, means for supplying oscillations to said circuit for combination with said rnwage waves to produce beats; a signal circuit connected to said receiving circuit, said signal circuit being for varying each of these currents in accordcombining ener iliary current with energy derived from said currents ofother frequencies, and a pluresponsive to the beats correspondin to one of said message waves and means in ividual thereto for causing each of the remainder of said mem'age waves 'to produce an indication.

19. A sign for supplying a plurality of messages transmitted by means of oscillations of different frequencies, means for supplying oscillations of asingle frequency for combmation'with the oscillations of said messages, and means for receiving said messages comprising means responsive to each of said combinations. v

20. In combination, means for producing a plurality of high frequency currents, means ance with a message, means for transmitting the ener tant station, a source of auxiliary current of frequency difi'erent from that of said varied currents, means at said distant station for from said'source of auxrality of selective means for simultaneously selecting different combination frequency components of said combined energy.

21. In combination, means for producing a plurality of high frequency currents, means for varying each of'these currents in accordance with a message, means for trans- .mitting the energy of said varied currents to a distant station, a local source at the dis-" "tantstation for supplying current of frequency different from. that of said varied currents, means for combining energy from said local current source with energy derived -from said currents of other frequencies, and a plurality of selective means for simultanealing system comprising means of said varied currents to a dissaid combined ener currents of other frequencies, and a plurality of selective means for simultaneously selecting different combination frequency components of said co'mbi'ned energy.

23. In combination, means for producing a plurality of :high frequency currents,

from said source of auxil- ,lary current wit energy derived from said means for varying each of these currents in accordance with a message, means for transmitt ing the energy of said varied currents to a distant station, a local source at the distant station for supplying current of frecurrents, common means at said distant stationfor selecting energy of all of the transmitted frequencies, means -for combining energy from said local, current source with energy derived from said currents of other frequencies, and a; plurality of selective means for simultaneously selecting different combination frequency components of subscribe In witness whereof, I hereunto my name this 1915.

'05 quency different from that of said varied f 8th day of September A. I).- l

EDWIN H'. coLPrr'rs. i I 

